1. Field of the Invention
This invention relates to a probe for an electrochemical oxygen measurement pickup having a solid, oxygen ion-conducting electrolyte with electrodes, and contact points at the end, which are connected to the electrodes in an electron-conducting manner.
2. Description of the Prior Art
Probes (sensor elements) for oxygen measurement pickups often consist of an ion-conducting solid-electrolyte tube which is closed on one end and the inner and outer surfaces of which are provided with electrodes. These electrodes extend up to the open end of the solid-electrolyte tube and form there the electrical contact points, from which the electric probe voltage is taken and is conducted to external terminals. If such measuring pickups are used, there is danger of false measurements, as the solid-electrolyte tube which usually protrudes transversely into the hot gas stream has a temperature gradient from its tip to its end and therefore has different ion conductivity. As a result, a voltage which decreases from the probe tip toward the end is delivered and the resultant electric voltage which is taken off at the contact points is thereby inaccurate and cannot be related unequivocally to a definite oxygen content of the gas to be measured.
If, in addition, the electrode exposed to the gas to be measured must be catalytically effective and must bring the gas components into chemical equilibrium, then the chemical equilibrium is adjusted differently along the probe in accordance with the temperature gradient. From this, different gas concentrations result and therefore, different electric electrode voltages (mixed potentials), which additionally falsify the electrical signal of the probe.